The proposed research has its long term goal elucidation of the contributions of Epstein-Barr virus (EBV) to the human cancers with which it is associated. Many observations indicated that EBV contributes to human lymphoid tumors by initiating and maintaining proliferation of the infected B-lymphocyte. Two of the viral proteins that appear essential for these events are Epstein-Barr nuclear antigen type 1 (EBNA-1) and latent membrane protein type 1 (LMP-1). During the current funding period biochemical properties and functions of EBNA-1 and LMP-1 have been identified. These properties and functions will be elucidated mechanistically in the research proposed in this application using many of the assays and reagents developed during the current funding period. EBNA- 1 is required for replication of EBV's genome as a plasmid in proliferating cells. The mechanism by which it supports plasmid replication will be established. The role that EBNA-1's linking function contributes to EBNA-1's support of replication and transcription will be analyzed. The hypothesis that this linking function contributes to the partitioning of viral genomes in proliferating cells will be tested. The second protein, LMP-1, has been hypothesize to behave as an oncogene by its constitutive signaling at the plasma membrane. The role of both the amino-terminal and carboxy-terminal cytoplasmic moieties of this onco- protein in signaling will be investigated. These studies on individual transforming genes of EBV will be complemented by the development of new methods to analyze EBV genetically so that insights gained from the study of specific viral genes can be extended readily to their study in the context of the whole virus.